1. Field of the Invention
The invention relates to an apparatus for ejecting a fluid material. In particular the invention relates to a syringe in which a pressurized hydraulic fluid is adapted to furnish the force necessary to eject a liquid a material.
Such a syringe is very useful when injecting a fluid, such as a liquid, into compact tissue where liquid diffusion is poor, such as for example, in bone tissue, as is often a problem in dental surgery. However, the syringe of the invention is not limited to this use and, on the contrary, extends by virtue of its novel design to a very wide variety of possible uses. In effect, the syringe also makes it possible to inject into soft tissue with the same softness and the same degree of precise control which one is able to achieve with purely manual syringes. Also, the syringe can be used for the injection of a liquid into tissue without a needle, by simple projection of the liquid under high pressure.
2. Description of Prior Art
Hydraulic syringes are known and are shown, for example, in U.S. Pat. No. 3,605,745 and in French Pat. No. 72 27030 (2,193,626). In these syringes The system comprises a hydraulic pressure system which itself comprises a piston on which a pressurized fluid acts. So as to provide most effective control over the pressure, the fluid is admitted on both sides of the piston and it is the differential pressure which is created between the two sides which causes the displacement of the piston in the direction of injection. The differential pressure occurs as a result of adjustment by the user of a blocking valve or of the opening of a drain orifice. This valve has a short extent. Furthermore, its open position is totally independent of the position of the jack piston, and, as a result, it is independent of the quantity of liquid to be injected. The user is, therefore, unaware of the actual speed of injection as well as the volume being injected at a given moment.